Integrating Apparent Conductance in Resistivity Sounding to Constrain 2D Gravity Modeling for Subsurface Structure Associated with Uranium Mineralization across South Purulia Shear Zone, West Bengal, India

South Purulia Shear Zone (SPSZ) is an important area for the prospect of uranium mineralization and no detailed geophysical investigations have been carried out in this region. To delineate the subsurface structure in the present area, vertical electrical soundings using Schlumberger array and gravity survey were carried out along a profile perpendicular to the SPSZ. Apparent conductance in the subsurface revealed a possible connection from SPSZ to Raghunathpur. The gravity model reveals the presence of a northerly dipping low density zone (most likely the shear zone) extending up to Raghunathpur under a thin cover of granitic schist of Chotanagpur Granite Gneissic Complex (CGGC). The gravity model also depicts the depth of the zone of density low within this shear zone at ~400？m near Raghunathpur village and this zone truncates with a steep slope. Integration of resistivity and gravity study revealed two possible contact zones within this low density zone in the subsurface at depth of 40？m and 200？m. Our study reveals a good correlation with previous studies in Raghunathpur area characterized by medium to high hydro-uranium anomaly. Thus the conducting zone coinciding with the low gravity anomaly is inferred to be a possible uranium mineralized zone. 1. Introduction Natural radioactive mineral deposits are found in suitable geological environment like shear zones [1–4], unconformity contacts, veins, and so forth [5, 6]. The mineralization may occur in vertical, dipping, and horizontal sheet-type structures. Uranium is highly conducting in nature and its presence in the subsurface provides good conductivity contrast between ore deposit and host rock [7, 8], making it possible to be delineated by electrical resistivity methods. Further, near surface structural features such as the shear zones can also be identified by detailed gravity measurements [9]. South Purulia Shear Zone (SPSZ) (Figure 1, after [10]) consists of mainly granite gneiss, amphibolites, phyllites, schist, carbonatite, and quartz-magnetite-apatite rocks and is of early mesoproterozoic age. Subsurface signature of uranium has been found in the existing apatite mine at Beldih but detailed geophysical activities are very limited in that area. Most of the previous studies deal with regional gravity and magnetic survey over the Eastern Indian Shield [11–13]. The Bouguer gravity anomaly map and magnetic data [14] suggest that there is a contrasting change from the Singhbhum Granite Craton in the south to the CGGC in the north but the detailed subsurface structure is little known in the present